Japanese encephalitis (JE) is a viral, mosquito-borne zoonotic infection caused by the JE virus (JEV).
Domestic pigs are the most important source of infection for mosquitoes that transmit JEV to humans in China, India, and Southeast Asia.
In the past decade 30,000-50,000 cases of JE have been notified to WHO with 10,000 deaths.
JE infection may result in asymptomatic disease, unspecific febrile disease, aseptic meningitis or acute encephalitis.
The case fatality rate is 30%, long-term disabilities occur in 25-50% of those surviving encephalitis.
There is no specific treatment for JE.
Three vaccines have been available for more than 50 years,
inactivated vaccines derived from mouse brain, which effectively controlled JE in Japan and other Asian countries. They may, however, cause angioedema and generalized urticaria;
inactivated vaccines cultivated on primary hamster kidney cells (PHK) and
live attenuated vaccine cultivated on primary hamster kidney cells.
Recently three new vaccines have been developed:
A live-attenuated vaccine based on strain SA14-14-2 has a good safety profile, effectiveness (88%-96%), and efficacy in large-scale trials (XX%).
Chimeric live-attenuated JE vaccine is a lyophilized formulation of a chimeric virus incorporating the structural genes (prM and E) from strain SA 14-14-2 into the non-structural genes of the yellow fever vaccine virus.
Inactivated JE vaccine (IC51, IXIARO) is a purified, formalin-inactivated, whole-virus vaccine grown on Vero-cell culture.